DNA translations/ protein synthesis

Overview of DNA translation • RNA “translates” the

genetic code from nucleotide bases into proteins.

• Each type of RNA plays a role in translation

• Translation happens after transcription

• 3 base sequences code for an amino acid– Proteins are made of amino

acids Think: how are you going to remember the difference between translation and transcription?

(‘scribe’ means to write)

Protein structureProtein structure

• Composed of building Composed of building blocks called amino blocks called amino acids.acids.– 20 different types of 20 different types of

amino acids.amino acids.– Sequence and length Sequence and length

of amino acid chain of amino acid chain determines the shape determines the shape of proteinsof proteins• The shape determines The shape determines

the characteristicsthe characteristics

Where Translation occurs Where Translation occurs • Translation occurs in the cytoplasm.Translation occurs in the cytoplasm.• Ribosomes assemble polypeptides. (chains of Ribosomes assemble polypeptides. (chains of

amino acids that form proteins)amino acids that form proteins)

Genetic Genetic codecode

• Each 3 nucleotides on Each 3 nucleotides on mRNA is a mRNA is a codoncodon..– Each codon codes Each codon codes

for a specific amino for a specific amino acid.acid.

– 64 possible codons.64 possible codons.– 1 start codons1 start codons– 3 stop codons3 stop codons– 60 different codons 60 different codons

code for 20 different code for 20 different types of amino types of amino acids.acids.

mRNA codon keymRNA codon key

Left side: reading from the inside out; What is a possible code for asparitic acid?

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Translation processTranslation process1.1. The ribosome binds to the messenger RNA.The ribosome binds to the messenger RNA.2.2. Transfer RNA (with anticodon) brings proper amino Transfer RNA (with anticodon) brings proper amino

acid to ribosome. (Anticodons are the acid to ribosome. (Anticodons are the complementary bases of the codons.)complementary bases of the codons.)

3.3. Ribosome moves to next three bases (codon).Ribosome moves to next three bases (codon).4.4. Another tRNA brings proper amino acid to ribosome.Another tRNA brings proper amino acid to ribosome.5.5. Protein is assembled.Protein is assembled.6.6. Stop codon signals end of protein.Stop codon signals end of protein.

Summary review

1. What monomers are proteins made of?

2. How many bases make up a codon?

3. Where does protein synthesis occur?

4. What is an anticodon?